Spacer-Receptor Systems Reverse Logic

LUMOPHORE-SPACER-RECEPTOR SYSTEMS (REVERSE LOGIC) 

Given the success of PET switches and sensors of the off-on type (Section 5), there is no fundamental reason why on-off systems cannot grow to be similarly useful. However there is little doubt that off-on systems are more visually appealing. Besides this aesthetic factor, off-on systems and especially the aminoalkyl aromatic family tend to be synthetically more accessible since amine synthons are available in great variety. 

Nevertheless, the example 17 has been available since 1989. This was the first case where all the optical and ion-binding parameters of a functioning device were quantitatively predictable from model compounds within experimental error. The only exception was the emission quantum yield of the switched- on state which deviated negatively by 30%. Part of this deviation was caused by the different solvent conditions which were necessary for examining the model lumophore. This was an illustration of rather exact molecular engineering since the specifications at 

LUMOPHORE-SPACER-RECEPTOR SYSTEMS WITH REDOX ACTIVE GUESTS 

Cu(II) is one of the best examples of a redox active guest, but apparently not when it is imprisoned in a cryptand such as 53. In this case, the Cu(II) is silent over a wide potential range during cyclic voltammetry. System 53 is designed as a lumophore-spacer-receptor system such as 28-30 and 33-34 in Section 1 with multiple lumophores. It also shows similar luminescence off-on switching with and even with Cu(II). The possibility of Cu(II) induced production of from moisture appears to have been ruled out. The absence of EET is a mystery which can only be dispelled by further studies on this interesting system. 

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